Original Zonk Machine Repair Overview

[@dibyamartandasamanta583]

You are a awesome guy , I can't believe you made your own Ge transistor despite being a small company .. I heard the story from my client regards to your Ge transistor. I got gifted one of your Yellow sunshine by my client for coding his website .

[@acidfuzzpedals9986]

I didn't do any of the hardcore engineering. That was all done by Ivan. I hope you're digging the Yellow Sunshine!

[@user-bp5uk7ku9b]

Glad you’re back, cheers

[@FretJunkies]

That’s some solid content man !!

[@soulmanvintagemuseum]

Does it catch a lot of RF on single coils too? I made my tribute pedal to the Zonk mk1 and getting quite noticeable zzzzzzz on fadings. Only the one thing I found to fix it is a brass shield box for the input jack socket because it's too close to the board when the enclosure is assembled. But how it used in the original units if they catch it too?

[@soulmanvintagemuseum]

And a really strange thing they used a lin 50k pot for the Attack biasing. Gary Hurst used log pots on his TB mk1 and it works really better here.

[@acidfuzzpedals9986]

The noise you're hearing when you assemble the enclosure isn't really due to RF, it's mainly EF and some EMF. Most builders assume this is just a very difficult circuit to "tune" and say that this or that transistor # as such is "too noisy" for the circuit and never understand what the fundamental issue is or know what an original is supposed to sound like. The original jumbo 3-piece Zonk enclosure is a very poor layout/design for this circuit and only exacerbates the problem (though it does LOOK cool). Your solution to shield the input with a grounded brass box is arguably the best in terms of preserving the original sound/tone. Even the MKI Tone Benders do this to some degree, the Zonk Machines more noticeably due to the high pass filter. You can select a transistor set and tune the noise out ~entirely, but you have to know what you're doing and have a very large quantity of transistors to choose from. For example another "experienced professional" builder who's emailed us about 100 times for advice on his builds (including questions like "does adding and LED cause noise?") commented that he won't use the TI 2G374 in the first position of a Zonk because it's "too noisy". Any builder worth one's salt knows that to manufacturers transistors only exist as data sheets. They can and do vary fairly widely in spec. while still being "within spec." You can't necessarily rely on date codes, epoxy color, dot color, tin/vs gold leads, etc...to determine this. You can run a frequency sweep and that will tell you something. He's probably got a batch of 2G374's with a higher frequency and doesn't realize it. This is kind of like the issue you told me about with your MK 1.5 build where you had problems biasing up the Mullard OC75. The very early production Mullard OC75's tend to be lower gain and leakage and are easier to bias up in that circuit. Regardless, in my opinion there were still much better choices than the OC75 for the MK 1.5. I think things moved very fast back in the 60's and sometimes being the first to do something and get it out in the world has it's drawbacks.

[@acidfuzzpedals9986]

@@soulmanvintagemuseum Exactly. I used logarithmic. Keeping it linear for the sake of originality is just silly.

[@soulmanvintagemuseum]

@@acidfuzzpedals9986 Absolutely agree about the original enclosure. If they place jack sockets at least 10mm far from the board. All could be much more stable. When I just shift a little the unscrewed top pard of the enclosure forward the noise disappeared. :) If they install the input socket on the left side and the output to the right it could solve a problem too. I tried. However it's a funny thing I found a decision in my case. Seems I decrease a lot the noise without a brass box. Firstly I stopped experimented with OC44 as a Q3 because I have only three ones and they sounds on my unit quite gated and very sensitive making more noise. I've took good old OC71. I have them a little more than three pieces and I found nice un-gated and thick-skinned as a noisemaker transistor. Then some placement turning of the input jack socket and looks like I have quite silent (I mean zzzzz) on fadings even with single coils. As Q1 I using now 2N1307 by TI. Glad to hear you are remember about my mk1.5. I finished with it. Found more suitable old OC75 for the Q1 but anyway I had to biased it a little decreasing 47K resistor. I just soldered suitable Piher resistor in parallel but under the stripboard ;)

[@soulmanvintagemuseum]

Amazing video, amazing new office :) What is that TI A02 hfe?

[@acidfuzzpedals9986]

I didn't pull the TI A02618. If it ain't broken don't fix it. You can make a common sense guess on the gain by cloning the circuit, then A/Bing and subbing gains until you're there. I'd say it's between 70-90hFE on this one, but I highly doubt they were all the same.

[@Dustyfingers]

Do you get those carbon comp resistors from eBay? Are you still making these replicas?

[@acidfuzzpedals9986]

All of the parts bins you see behind me came from an estate sale. Back in ~2009 Kristina wanted me to get up at the ass crack of dawn to go estate sale shopping with her. I really didn't want to, but she said "there's going to be electronics", so I went. After hours of looking at purses, women clothes, and other random junk we arrived at a warehouse. It turned out that three electrical engineering firms were liquidating their "obsolete" stock. I almost shit my pants and didn't even know where to start, as it was full of all the parts you see in my office, vintage germanium and silicon transistors, caps, etc.... The lady running the liquidation didn't know anything about electronics and was going to junk whatever didn't sell. Kristina and her got to talking while I ran around trying to figure out how to fit things in the car. The lady said that for $50 bucks I can take whatever I want. We loaded the car so full I even had boxes on my lap! As we were pulling away Kristina asked if I wanted to go back for an item, I told Kristina to" just drive!" as I couldn't believe what happened. I felt like I had robbed a bank and wouldn't believe it was real until I actually made it back to the shop. Long story short, I didn't get them on eBay.

[@Dustyfingers]

Acid Fuzz Pedals best story ever! Had a similar experience when I bought an Echoplex ep2 for $100 in rural iowa

[@acidfuzzpedals9986]

Nice score! I guess sometimes the universe lets us know when we're on the right path.

[@smc1868]

I’m a mechanical man I do the best I caaaan